Sample size The sample size requirements for this study are intended to provide adequate power for the analysis of the primary objective ( decrease event-related mortality). The simulation were run in statsoft six sigma software according to the following hypotheses: the mortality of severe brain injury used as a Null hypothesis was 58%. This percent value is expected to decrease at 40% in the study arm. The target type-I error(α) was 0.05. A sample size of 119 patients per group would allow a power of 80% to detect an individual risk score ratio of 0.70 with a type -I error of 0.05.